**Neither a teacher nor a native speaker.**
Hello dear guest:
First off: Sentences begin with Capital letters and end with. ! or ?
About your question:
I believe the 2nd sentence is not correct.
It must be:
We are giving a chance to prove something. -> Present Progressive
We have given a chance to prove something. -> Present Perfect Simple
Sentence 1 starts now.
Sentence 2 started in the past and is still active.
(Last week you started to give them a chance and today you're still giving them a chance.)
I have a question to the other members:
Could it be possible that "are giving" (or even "are given"?) makes the sentence to a passive one?
I hope I could help you